The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.
Lameness is a symptom of common musculoskeletal injuries and/or disease in quadruped animals such as domestic dogs and cats. For example, various kinds of ligament and tendon injuries, degenerative joint diseases, insidious bone diseases and other ailments may be manifested in lameness. In this context, lameness refers to the inability of an animal to walk in a normal fashion or to bear full weight on all the limbs in the manner typically observed or experienced in a healthy condition.
However, at present, detecting lameness usually is performed in ways that have significant drawbacks. A first approach involves visual observation and estimation of gait or movement followed by evaluation of an animal's response to stimulus. This approach involves subjective individual analysis that is prone to error and usually only can identify large changes in lameness and/or load bearing starting at higher grades of lameness. It is inherently non-scientific and imprecise.
Another approach involves using a stationary force plate or force pad, alone or in conjunction with secondary quantitative analysis such as goniometry and/or limb circumference measurements. Kinetic analysis based on data from a force plate can be used to generate force time curves in three dimensions as well as values for peak vertical force (PVF), defined as the maximum force in the vertical dimension. These data can be used to evaluate craniocaudal direction in the sense of propulsion and braking, and mediolateral direction or turning. However, the data gathering apparatus is costly, esoteric in nature, and requires detailed training of the subject animal to ensure that load cells are struck and velocity is constant. Furthermore, the apparatus does not measure stride length or duration and is difficult to set up.
Force pads can be used for temporospatial gait analysis to indicate the duration of phases of stride, stride velocity, stride length, step length and a total pressure index. Duration of phases of stride refers to distinguishing stance versus swing. Stride length can be measured as the distance between paw strikes of the same limb. Step length can comprise the distance from an aspect of paw strike of one limb to the same aspect of the strike of a paw of a contralateral limb. The total pressure index may be the sum of peak pressure values recorded on the pad from each activated sensor by a paw during mat contact; it is related but not equal to peak vertical force. Force pad apparatus also is costly, requires a large physical space, and is esoteric. Additional forces present during ambulation can interfere with and complicate measurement; examples include forces to change speed, direction or maintain balance. Further, the apparatus only measures total ground reaction forces and not component vectors.
Kinematic gait analysis typically involves using markers affixed to joints and recording the movement of the markers using a video camera, followed by secondary quantitative analysis such as goniometry and/or limb circumference measurements. This approach is costly, difficult or impractical to perform with some animals, and produces data that is not easily repeatable. There can be random error in the data due to skin movement, and creating reference values is not supported.
Based on these deficiencies in current practice, there is a need for an improved easily available apparatus for reliably and precisely quantitating lameness in animals.